ABSTRACT
This chapter discusses the differential response of individuals and populations exposed to heavy metals or metalloids and evidence for the evolution of tolerance in exposed populations. It explores the evolution of metal tolerance in aquatic organisms, and discusses approaches used to detect natural selection and the evolution of metal tolerance. Genetic factors can significantly affect the response of individuals or populations exposed to metal pollution. Genetically based tolerance is not lost when individuals are placed into clean environments and is inherited by offspring regardless of whether they are reared in polluted or nonpolluted environments. If tolerance to metal exposure is genetically based, the survivors will constitute a population with an altered genetic composition relative to the preexposure population. Retention of tolerance in animals taken from contaminated sites and maintained in clean conditions is evidence that the tolerance is genetically determined and not acclimation to prevailing conditions.
